Lake Organisms Adaptations

Question 1

Draw the fitness function. You have to include: Optimal trait value, mean trait value, fitness variance, and phenotypic variance.

Question 2

How does phytoplankton stay planktonic?

Answer 2

Small particles sink more slowly than large particles
Adaptations to reduce sinking rate
* Density- vacuoles, gas vesicles,
ballast molecules, mucus
* Size/Shape - forming colonies,
spines
* Motility -flagella

Question 3

There are 3 types of zooplankton, what are they?

Answer 3

• Rotifers – filter feeders, some are predatory
• Crustaceans
  – Cladocerans – principal grazers on phytoplankton
  – Copepods – some are omnivores, some predators
• Insects
  – Chaoborus (Phantom midge larvae) – important
  predator

Question 4

What is planktivorous fish, and what is their preferred food?

Answer 4

• Consume zooplankton throughout their lives
• Often feed in a size-selective way, consuming
  the largest zooplankton (often Daphnia)

Question 5

What is piscivorous fish, and what us their preferred food?

Answer 5

• Consume zooplankton when young
• Undergo an ontogenetic niche shift to consuming fish